Here's how Dring describes it: "If you just imagine a bench with ... a mat on it, and then we just sew the seeds onto that mat. And then underneath the lights, the roots grow into the mat that's in the tray, and then every 12 hours, water waters the mat again, and under the light it grows, so no soil is required."

Sunlight, of course, doesn't reach that far underground. So Dring and Ballard use LED lights as a substitute. Dring says LED lights have evolved so much that you can pick and choose elements of the light spectrum to get something that's identical to the sun.

Those lights require energy, but to ensure the project truly is "zero carbon," they're buying it from a company that gets all of its energy from wind and solar.

As for what's under cultivation way down there, Dring says they've got arugula, lettuce and microherbs like coriander, mustard leaf and tatsoi.

One day, they might also grow tomatoes, which Dring assures would be very tasty, despite the fact that they're hydroponic.

Chef Roux's "palate is pretty damn good," says Dring. "Selling a homogenous, sort of tasteless tomato is certainly not part of our plans."

Besides a commitment to good flavor, Dring says he's hopeful the venture will succeed because the vegetables can reach consumers far more quickly than those grown on a farm.

"Obviously as soon as you cut product, it starts to degrade in flavor," says Dring. "We can get it to the market in from field to fork, in four to eight hours. Usually it travels 72 hours, maybe four or five days. That's what's really interesting to our customers and wholesalers — that's what's turning them on."

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RENEE MONTAGNE, HOST:

Our next story takes us 10 stories underground. During World War II, Londoners would descend spiral staircases into tunnels to escape German bombs. Now, one of those long, empty air raid shelters is filled with fresh greens, thanks to businessman Steven Dring.

STEVEN DRING: It's a nice sort of warm duvet of insulation for growing produce down there.

MONTAGNE: Steven Dring and his partner turned the tunnel into a vegetable farm. He described how it works.

DRING: If you just imagine a bench with what is a sort of mat on it, and then we just sow the seeds onto that mat, and then underneath the lights, the roots grow into the mat that's in the tray. And then every sort of 12 hours, water waters them out again, and under the light, it grows. So, no solar is required.

MONTAGNE: What about the light? I mean, it has to substitute for sunlight.

DRING: Yeah, the LED lights, they're now at the level where you can actually sort of emphasize and suppress elements of the light spectrum. So, it's acting in exactly the same way as sunlight, and it produces exactly the same light spectrum as sunlight. So, you can emphasize if it's the blue spectrum or the red spectrum, and it just produces a light spectrum identical to the sun.

MONTAGNE: Well, your company is called Zero Carbon Food. Even the lights, I would have thought, would take up some amount of energy. I mean, how perfectly energy efficient are you?

DRING: We are zero-carbon because, yes, there's energy required for the lighting, but we actually get all of the energy supplied from a green energy company that gets all of their energy from wind and solar. So, it's a green energy supply that feeds our lighting system.

MONTAGNE: So, what exactly are you growing down there?

DRING: So, we are growing - you guys call it arugula. And we're growing sort of standard (unintelligible) lettuce. We are growing microherbs, which are sort of miniature coriander, tatsoi, pak choi, mustard leaf.

MONTAGNE: You know, there's one thing - and this may be one vegetable that just ruined it for the rest - by hydroponic tomatoes, when they sort of came along, were known as being rather without taste.

DRING: Yeah. I don't know what happened there, in terms of tomatoes. But the thing that affects the actual product is the light, the seeds, the CO2 and the heat. And so if they have been sort of grown in the past and given hydroponics a bad name, then, yeah, I think people are just growing the wrong strain and the wrong variety of tomato.

MONTAGNE: But, at this point, you haven't had, you know, the bad reputation of the tomato. Has it made it problematic for you to sell these to restaurants and people, generally?

DRING: No, not in the slightest. We've had some - obviously, we got a high-quality chef onboard, a two-Michelin star chef. So, yeah, his palate's pretty damn good when it comes to actually tasting our greens at the moment. But if we do end up growing tomatoes that don't pack that flavor and pack that punch, we will just stop doing them and move onto the next product. Selling a homogenous, sort of tasteless tomato is certainly not part of our plans.

MONTAGNE: Why would people want to buy these hydroponic vegetables that are grown way down below the ground? I mean, what's your selling point?

DRING: The fact that we are local to the markets. Obviously, as soon as you cut a product, then it starts to degrade in flavor. So, we can get into the markets and get it basically from field to fork within, sort of, four to eight hours, whereas usually it travels for sort of 72 hours, and sometimes maybe four or five days. And that's what's really interesting to our wholesalers and customers. That's what's turning them on.

MONTAGNE: Boy, I should say so. I hadn't really thought of that, but the restaurants are just above you.

DRING: Exactly. It's the logistics that do it.

MONTAGNE: Well, very nice. Thank you very much.

DRING: You're very welcome.

MONTAGNE: Steven Dring is cofounder of Zero Carbon Food. He spoke to us from London. Transcript provided by NPR, Copyright NPR.